RU2804732C2 - Method and device for image encoding/decoding for transmission of color signal component prediction in service signals according to whether palette mode is applicable or not, and method for bit stream transmission - Google Patents

Abstract

FIELD: image processing.

SUBSTANCE: invention is related to encoding/decoding images for transmission in service signals of prediction information of components of color signals. An image decoding method is proposed, which is carried out by means of image decoding equipment, and contains: determining the current block by splitting an image; identifying whether or not a palette mode is applied to the current block based on the palette mode flag obtained from the bitstream; obtaining palette mode encoding information of the current block from the bit stream based on the tree type of the current block and whether or not palette mode is applied to the current block; and obtaining chroma component prediction information of the current block from the bitstream based on a palette mode not applied to the current block.

EFFECT: increase of efficiency of encoding/decoding by transmitting prediction information of color signal components in service signals.

11 cl, 1 tbl, 26 dwg

Description

Field of technology to which the invention relates

[1] The present disclosure relates to an image encoding/decoding method and equipment, and more specifically, to a method for encoding/decoding images to carry in signaling signals the prediction information of chrominance signal components depending on whether or not to apply a palette mode, and to a method for transmitting a bit stream generated by an image encoding method/equipment of the present disclosure.

State of the art

[2] Recently, the demand for high-quality, high-definition images, such as high-definition (HD) images and ultra-high-definition (UHD) images, has been increasing in various fields of technology. As the resolution and quality of image data increases, the amount of transmitted information or bits increases relatively compared to existing image data. Increasing the amount of information or bits transmitted results in increased transmission costs and storage costs.

[3] Accordingly, there is a need for high-performance image compression technology for efficiently transmitting, storing and reproducing information regarding high-quality, high-resolution images.

The essence of the invention

Technical problem

[4] The purpose of the present disclosure is to provide an image encoding/decoding method and equipment with improved encoding/decoding efficiency.

[5] The purpose of the present disclosure is to provide an image encoding/decoding method and equipment for improving encoding/decoding efficiency by signaling the prediction information of chrominance signal components depending on whether or not to use a palette mode.

[6] Another object of the present disclosure is to provide a method for transmitting a bit stream generated by an image encoding method or equipment according to the present disclosure.

[7] Another object of the present disclosure is to provide a recording medium storing a bitstream generated by an image encoding method or equipment according to the present disclosure.

[8] Another object of the present disclosure is to provide a recording medium storing a bitstream received, decoded, and used to reconstruct an image by the image decoding equipment according to the present disclosure.

[9] The technical problems addressed by the present disclosure are not limited to the above technical problems, and other technical problems not described herein should become apparent to those skilled in the art from the following description.

Technical solution

[10] An image decoding method performed by the image decoding equipment according to an aspect of the present disclosure may comprise determining a current block by dividing the image, identifying whether or not a palette mode is applied to the current block based on a palette mode flag obtained from the bitstream, obtaining palette mode encoding information of the current block from the bit stream, based on the tree type of the current block and whether palette mode is applied or not for the current block, and obtaining prediction information of the chrominance signal components of the current block from the bit stream, based on the palette mode not applying for the current block.

[11] In addition, the image decoding equipment according to an aspect of the present disclosure may include a storage device and at least one processor. The at least one processor may determine the current block by dividing the image, identify whether or not a palette mode is applied to the current block based on a palette mode flag obtained from the bit stream, obtain palette mode encoding information of the current block from the bit stream, based on the tree type of the current block and whether or not a palette mode is applied to the current block, and obtain prediction information for chrominance signal components of the current block from the bitstream based on the palette mode not applied to the current block.

[12] In addition, the image encoding method carried out by the image encoding equipment according to an aspect of the present disclosure may comprise determining a current block by dividing the image, determining a prediction mode of the current block, encoding a palette mode flag indicating whether the current block's prediction mode is or not a palette mode, based on whether the current block's prediction mode represents or not a palette mode, encoding palette mode encoding information in which the current block is palette-mode encoded, based on the tree type of the current block, and whether the current block's prediction mode represents block is a palette mode or not, and encoding prediction information of chrominance signal components of the current block based on the prediction mode of the current block not being a palette mode.

[13] In addition, the transmission method according to another aspect of the present disclosure may transmit a bit stream generated by the image encoding equipment or the image encoding method of the present disclosure.

[14] In addition, the computer-readable recording medium according to another aspect of the present disclosure can store a bit stream generated by the image encoding equipment or the image encoding method of the present disclosure.

[15] The features briefly summarized above with respect to the present disclosure are merely exemplary aspects of the following detailed description of the present disclosure and do not limit the scope of the present disclosure.

Advantages of the invention

[16] According to the present disclosure, it is possible to provide an image encoding/decoding method and equipment with improved encoding/decoding efficiency.

[17] In addition, according to the present disclosure, it is possible to provide an image encoding/decoding method and equipment for improving encoding/decoding efficiency by signaling the prediction information of chrominance signal components depending on whether or not palette mode is to be applied.

[18] In addition, according to the present disclosure, it is possible to provide a method for transmitting a bitstream generated by an image encoding method or equipment according to the present disclosure.

[19] In addition, according to the present disclosure, it is possible to provide a recording medium storing a bit stream generated by the image encoding method or equipment according to the present disclosure.

[20] In addition, according to the present disclosure, it is possible to provide a recording medium storing a bitstream received, decoded, and used to reconstruct an image by the image decoding equipment according to the present disclosure.

[21] Those skilled in the art will appreciate that the advantages that may be achieved through the present disclosure are not limited to those specifically described above, and other advantages of the present disclosure will be more clearly understood from the detailed description.

Brief description of drawings

[22] FIG. 1 is a view schematically showing a video encoding system to which an embodiment of the present disclosure is applicable.

[23] FIG. 2 is a view schematically showing image encoding equipment to which an embodiment of the present disclosure is applicable.

[24] FIG. 3 is a view schematically showing image decoding equipment to which an embodiment of the present disclosure is applicable.

[25] FIG. 4 is a view showing an image segmentation structure according to the embodiment.

[26] FIG. 5 is a view showing an embodiment of a block segmentation type according to a multi-type tree structure.

[27] FIG. 6 is a view showing a signaling mechanism for blocking information in a quadtree with a nested multi-type tree structure according to the present disclosure.

[28] FIG. 7 is a view showing an embodiment in which a CTU is segmented into multiple CUs.

[29] FIG. 8 is a view illustrating an embodiment of a redundant split pattern.

[30] FIG. 9 is a view illustrating a syntax for signaling chrominance signal formats according to an embodiment.

[31] FIG. 10 is a view illustrating a chrominance signal format classification table according to an embodiment.

[32] FIG. 11 is a view illustrating horizontal scanning and vertical scanning according to the embodiment.

[33] FIG. 12-13 are views illustrating syntax for palette mode according to an embodiment.

[34] FIG. 14-19 are views illustrating syntax for palette mode according to an embodiment.

[35] FIG. 20 is a view illustrating an equation for determining PredictorPaletteEntries and CurrentPaletteEntries according to an embodiment.

[36] FIG. 21 is a view illustrating the syntax of an encoding unit according to the modified embodiment.

[37] FIG. 22 is a flowchart illustrating a method for transmitting predetermined intra-chrominance signal prediction information in signaling signals according to an embodiment.

[38] FIG. 23 is a flowchart illustrating a method for obtaining chrominance signal prediction information by decoding equipment according to the embodiment.

[39] FIG. 24 is a flowchart illustrating a method for encoding an image by the encoding equipment according to the embodiment.

[40] FIG. 25 is a flowchart illustrating a method for decoding an image by the decoding equipment according to the embodiment.

[41] FIG. 26 is a view showing a content streaming system to which an embodiment of the present disclosure is applicable.

Optimal mode for carrying out the invention

[42] Embodiments of the present disclosure are described in detail hereinafter with reference to the accompanying drawings so that they can be easily implemented by those skilled in the art. However, the present disclosure may be implemented in a variety of forms and is not limited to the embodiments described herein.

[43] In describing the present disclosure, if it is determined that a detailed description of a related known function or construct would cause unnecessary ambiguity to the scope of the present disclosure, the detailed description thereof is omitted. In the drawings, parts not related to the description of the present disclosure are omitted, and like reference numbers are added to like parts.

[44] In the present disclosure, when a component is “connected,” “coupled,” or “linked” to another component, this may include not only a direct connection-based relationship, but also an indirect connection-based relationship in which an intermediate component is present. In addition, when a component “includes” or “has” other components, it means that other components may be additionally included, not the exclusion of other components, unless otherwise noted.

[45] In the present disclosure, the terms “first”, “second”, etc. may be used only for the purpose of distinguishing one component from other components and does not limit the order or importance of the components unless otherwise noted. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a “second component” in another embodiment, and likewise, a second component in one embodiment may be referred to as a “first component” in another embodiment.

[46] In the present disclosure, components that are different from each other are intended to clearly describe each feature and do not mean that the components are necessarily separate. Thus, multiple components may be integrated and implemented in a single hardware or software module, or a single component may be distributed and implemented in multiple hardware or software modules. Therefore, even if not stated otherwise, such embodiments in which components are integrated or a component is distributed are also included within the scope of the present disclosure.

[47] In the present disclosure, the components described in the various embodiments do not necessarily mean essential components, and some components may be optional components. Accordingly, an embodiment consisting of a subset of the components described in the embodiment is also included within the scope of the present disclosure. In addition, embodiments including other components in addition to the components described in the various embodiments are included within the scope of the present disclosure.

[48] The present disclosure relates to image encoding and decoding, and the terms used in the present disclosure may have a general meaning commonly used in the art to which the present disclosure pertains, unless defined for the first time in the present disclosure.

[49] In the present disclosure, "frame" generally means a unit representing one image at a particular time period, and a slice/tile is an encoding unit constituting part of a frame, and one frame may consist of one or more slices/ tiles In addition, a slice/tile may include one or more coding tree units (CTUs).

[50] In the present disclosure, "pixel" or "pixel" can mean the smallest unit constituting one frame (or image). In addition, "sample" can be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel/pixel value of a luma component or only a pixel/pixel value of a chrominance signal component.

[51] In the present disclosure, a "unit" may represent a basic unit of image processing. The unit may include at least one of a specific frame area and information associated with the area. The unit may be used interchangeably with terms such as "sample array", "block" or "zone" in some cases. In general, an MxN block may include samples (or arrays of samples) or a set (or array) of transform coefficients of M columns and N rows.

[52] In the present disclosure, "current block" may mean one of "current encoding block", "current encoding unit", "target encoding block", "target decoding block" or "target processing block". When prediction is performed, "current block" may mean "current prediction block" or "target prediction block". When transform (inverse transform)/quantization (dequantization) is performed, "current block" can mean "current transform block" or "transform target block". When filtering is performed, "current block" can mean "target filtering block".

[53] In addition, in the present disclosure, "current block" may mean "the luma block of the current block" unless explicitly referred to as a chrominance block. The "current block chrominance block" may be expressed by including an explicit description of the chrominance block, such as "chroma block" or "current chroma block".

[54] In the present disclosure, the terms "/" and "" are to be interpreted to indicate "and/or". For example, the expression "A/B" and "A, B" can mean "A and/or B". Additionally, "A/B/C" and "A/B/C" may mean "at least one of A, B and/or C".

[55] In the present disclosure, the term “or” should be interpreted to indicate “and/or.” For example, the expression "A or B" may contain 1) only "A", 2) only "B", and/or 3) "both A and B". In other words, in the present disclosure, the term “or” is to be interpreted as indicating “in addition or alternatively.”

[56] Video Coding System Overview

[57] FIG. 1 is a view showing a video encoding system according to the present disclosure.

[58] The video encoding system according to an embodiment may include encoding equipment 10 and decoding equipment 20. Encoding equipment 10 may deliver encoded information or video and/or image data to decoding equipment 20 in the form of a file or streaming via a digital storage medium or network.

[59] The encoding equipment 10 according to an embodiment may include a video source generator 11, an encoding unit 12, and a transmitter 13. The decoding equipment 20 according to an embodiment may include a receiver 21, a decoding unit 22, and a rendering unit 23. The encoding unit 12 may be referred to as a “video/image encoding unit,” and the decoding unit 22 may be referred to as a “video/image decoding unit.” The transmitter 13 may be included in the encoding module 12. The receiver 21 may be included in the decoding module 22. The rendering module 23 may include a display, and the display may be configured as a separate device or an external component.

[60] The video source generator 11 may obtain video/image through a video/image capturing, synthesizing, or shaping process. The video source generator 11 may include a video/image capture device and/or a video/image generation device. The video/image capturing device may include, for example, one or more cameras, video/image archives including previously captured video/images, and the like. The video/image generating apparatus may include, for example, computers, tablet computers and smartphones and may (electronically) generate video/images. For example, a virtual video/image may be generated via a computer or the like. In this case, the video/image capturing process can be replaced by the associated data generation process.

[61] The encoding unit 12 can encode the input video/image. The encoding unit 12 may perform a series of procedures such as prediction, transform and quantization for compression and encoding efficiency. The encoding unit 12 can output encoded data (encoded video/image information) in the form of a bit stream.

[62] The transmitter 13 may transmit encoded information or video/image data output in the form of a bit stream to the receiver 21 of the decoding equipment 20 via a digital storage medium or a network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-Ray, HDD, SSD, and the like. The transmitter 13 may include an element for generating a multimedia file through a predefined file format and may include an element for transmission through a broadcast/communications network. The receiver 21 may retrieve/receive a bit stream from the storage medium or network and transmit the bit stream to the decoding unit 22.

[63] The decoding unit 22 can decode the video/image by performing a series of procedures such as dequantization, deconversion and prediction corresponding to the operation of the encoding unit 12.

[64] The rendering unit 23 may prepare a decoded video/image by rendering. The video/image prepared by rendering can be displayed through the display.

[65] General introduction to image encoding equipment

[66] FIG. 2 is a view schematically showing image encoding equipment to which an embodiment of the present disclosure is applicable.

[67] As shown in FIG. 2, the image encoding equipment 100 may include an image segmentation unit 110, a subtractor 115, a converter 120, a quantizer 130, a dequantizer 140, an inverse converter 150, an adder 155, a filter 160, a memory 170, an inter-prediction unit 180, an intra-prediction unit 185 and an entropy encoder 190. The inter-prediction module 180 and the intra-prediction module 185 may be collectively referred to as a “prediction module”. Converter 120, quantizer 130, dequantizer 140, and inverse converter 150 may be included in the residual processor. The residual processor may further include a subtractor 115.

[68] All or at least a portion of the plurality of components configuring image encoding equipment 100 may be configured by a single hardware component (eg, an encoder or processor) in some embodiments. In addition, storage device 170 may include a decoded frame buffer (DPB) and may be configured with a digital storage medium.

[69] The image segmentation module 110 may segment an input image (either a frame or a movie frame) input to the image encoding equipment 100 into one more processing unit. For example, the processing unit may be called a "coding unit (CU)". A coding unit may be obtained by recursively segmenting a coding tree unit (CTU) or largest coding unit (LCU) according to a quadtree, binary tree, and ternary tree (QT/BT/TT) structure. For example, one coding unit may be segmented into multiple coding units of greater depth based on a quadtree structure, a binary tree structure, and/or a ternary structure. To segment a coding unit, a quadtree structure may first be applied, and subsequently a binary tree structure and/or a ternary structure may be applied. The encoding procedure of the present disclosure may be performed based on a final encoding unit that is no longer segmented. The largest coding unit may be used as the final coding unit, or a coding unit of greater depth obtained by segmenting the largest coding unit may be used as the final coding unit. Here, the encoding procedure may include a prediction, transformation and reconstruction procedure, which is described below. As another example, the processing unit of the encoding procedure may be a prediction unit (PU) or a transformation unit (TU). The prediction unit and the transformation unit may be split or segmented from the final encoding unit. The prediction unit may be a sample prediction unit, and the transformation unit may be a unit for extracting a transformation coefficient and/or a unit for extracting a residual signal from the transformation coefficient.

[70] The prediction module (inter-prediction module 180 or intra-prediction module 185) may perform prediction regarding a block to be processed (the current block) and generate a predicted block including prediction samples for the current block. The prediction module may determine whether intra prediction or inter prediction is applied based on the current block or CU. The prediction module may generate various information related to prediction of the current block and transmit the generated information to the entropy encoder 190. Information regarding the prediction may be encoded in the entropy encoder 190 and output in the form of a bit stream.

[71] The intra prediction module 185 may predict the current block by reference to the samples in the current frame. Samples for reference may be located in the surroundings of the current block or may be spaced apart according to an intra-prediction mode and/or intra-prediction technology. The intra prediction modes may include a plurality of non-directional modes and a plurality of directed modes. The omnidirectional mode may include, for example, DC mode and planar mode. The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the granularity of the prediction direction. However, this is merely an example; more or less directional prediction modes may be used depending on the setting. The intra prediction module 185 may determine the prediction mode applied to the current block by using the prediction mode applied to the adjacent block.

[72] The inter-prediction unit 180 may extract a predicted block for the current block based on a reference block (an array of reference samples) indicated by a motion vector for the reference frame. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0-prediction, L1-prediction, bi-prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block present in the current frame and a temporal neighbor block present in the reference frame. The reference frame including the reference block and the reference frame including the temporary adjacent block may be identical or different. A temporary neighbor block may be referred to as a "co-located reference block", "co-located CU (colCU)", or the like. A reference frame including a temporary adjacent block may be referred to as a "co-located frame (colPic)". For example, the inter-prediction module 180 may configure a list of motion information candidates based on neighboring blocks and generate information indicating which candidate is used to retrieve the motion vector and/or reference frame index of the current block. Mutual prediction can be performed based on different prediction modes. For example, in the case of the skip mode and the merge mode, the inter-prediction unit 180 may use the motion information of a neighboring block as the motion information of the current block. In the case of the skip mode, unlike the combine mode, the residual signal may not be transmitted. In the case of the motion vector prediction (MVP) mode, the motion vector of an adjacent block can be used as a motion vector predictor, and the motion vector of the current block can be signaled by encoding the motion vector difference and an indicator for the motion vector predictor. The motion vector difference may mean the difference between the motion vector of the current block and the motion vector predictor.

[73] The prediction module can generate a prediction signal based on various prediction methods and prediction technologies described below. For example, the prediction module may not only apply intra-prediction or inter-prediction, but also simultaneously apply both intra-prediction and inter-prediction to predict the current block. A prediction method that simultaneously uses both intra prediction and inter prediction to predict the current block may be called "combined inter and intra prediction (CIIP)". In addition, the prediction module can perform intra-block copying (IBC) to predict the current block. In-block copying can be used to encode game image/video content and the like, such as screen content encoding (SCC). IBC is a method of predicting the current frame using a previously reconstructed reference block in the current frame at a location spaced from the current block by a predetermined distance. When IBC is applied, the location of the reference block in the current frame can be encoded as a vector (block vector) corresponding to a predetermined distance. IBC essentially performs prediction within the current frame, but can be performed similarly to inter-prediction in that the reference block is retrieved within the current frame. Thus, the IBC may use at least one of the inter-prediction technologies described in the present disclosure.

[74] The prediction signal generated by the prediction module can be used to generate a reconstructed signal or generate a residual signal. The subtractor 115 may generate a residual signal (a residual block or an array of residual samples) by subtracting a prediction signal (a prediction block or an array of prediction samples) output from the prediction module from an input image signal (a source block or an array of original samples). The generated residual signal can be transmitted to the converter 120.

[75] Converter 120 can generate conversion coefficients by applying conversion technology to the residual signal. For example, the transform technology may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loeve transform (KLT), a graph-based transform (GBT), or a conditionally nonlinear transform (CNT). ). Here, GBT means a graph-derived transformation when the relationship information between pixels is represented by the graph. CNT means the transformation obtained from the prediction signal generated using all the previously reconstructed pixels. In addition, the conversion process can be applied to square pixel blocks that are identical in size, or can be applied to blocks that are variable in size rather than square.

[76] Quantizer 130 may quantize the transform coefficients and pass them to entropy encoder 190. Entropy encoder 190 may encode the quantized signal (information regarding the quantized transform coefficients) and output a bit stream. Information regarding the quantized transform coefficients may be referred to as "residual information". Quantizer 130 may re-arrange the quantized transform coefficients in block form into one-dimensional vector form based on the scan order of the coefficients, and generate information regarding the quantized transform coefficients based on the quantized transform coefficients in one-dimensional vector form.

[77] Entropy encoder 190 may implement various encoding techniques, such as, for example, exponential Golomb coding, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and the like. Entropy encoder 190 may encode information needed to reconstruct video/images other than quantized transform coefficients (eg, syntax element values, etc.), together or separately. Encoded information (eg, encoded video/image information) may be transmitted or stored in network abstraction layer (NAL) units in the form of a bit stream. The video/image information may further include information regarding various parameter sets, such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. The signaling information, transmission information, and/or syntax elements described in the present disclosure may be encoded through the encoding procedure described above and included in the bit stream.

[78] The bitstream may be transmitted over a network or may be stored on a digital storage medium. The network may include a broadcast network and/or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-Ray, HDD, SSD, and the like. A transmitter (not shown) transmitting the signal output from the entropy encoder 190 and/or a storage module (not shown) storing the signal may be included as an internal/external element of the encoding equipment 100, and alternatively, the transmitter may be included in the entropy encoder 190 .

[79] The quantized transform coefficients output from quantizer 130 can be used to generate a residual signal. For example, a residual signal (residual block or residual samples) may be recovered by applying dequantization and inverse transform to the quantized transform coefficients via dequantizer 140 and inverse transformer 150.

[80] An adder 155 adds the reconstructed residual signal with the prediction signal output from the inter-prediction module 180 or the intra-prediction module 185 so as to generate a reconstructed signal (reconstructed frame, reconstructed block, reconstructed sample array). If there is no remainder for a block to be processed, for example in a case in which the skip mode is applied, the predicted block can be used as a reconstructed block. The adder 155 may be referred to as a "recovery module" or a "recovered block generator." The generated reconstructed signal can be used to internally predict the next block to be processed in the current frame, and can be used to inter-predict the next frame through filtering, as described below.

[81] Filter 160 may enhance the subjective/objective quality of images by applying filtering to the reconstructed signal. For example, filter 160 may generate a modified reconstructed frame by applying various filtering techniques to the reconstructed frame and store the modified reconstructed frame in storage device 170, namely, a DPB of storage device 170. Various filtering techniques may include, for example, deblocking filtering. , sampled adaptive bias, adaptive loop filter, bilateral filter, etc. The filter 160 may generate various filtering-related information and transmit the generated information to the entropy encoder 190, as described below in the description of each filtering method. Information associated with filtering may be encoded by entropy encoder 190 and output in the form of a bitstream.

[82] The modified reconstructed frame transferred to the storage device 170 can be used as a reference frame in the inter-prediction module 180. When mutual prediction is applied through the image encoding equipment 100, prediction mismatch between the image encoding equipment 100 and the image decoding equipment can be eliminated, and encoding efficiency can be improved.

[83] The DPB of the storage device 170 may store the modified reconstructed frame for use as a reference frame in the inter-prediction module 180 . The storage device 170 may store block motion information from which motion information in the current frame is retrieved (or encoded) and/or motion information of blocks in a frame that have already been reconstructed. The stored motion information may be transmitted to the inter-prediction unit 180 and used as spatial neighbor block motion information or temporal neighbor block motion information. Memory 170 may store reconstructed samples of reconstructed blocks in the current frame and may transmit reconstructed samples to intra prediction module 185.

[84] General introduction to image decoding equipment

[85] FIG. 3 is a view schematically showing image decoding equipment to which an embodiment of the present disclosure is applicable.

[86] As shown in FIG. 3, the image decoding equipment 200 may include an entropy decoder 210, a dequantizer 220, an inverse converter 230, an adder 235, a filter 240, a memory 250, an inter-prediction unit 260, and an intra-prediction unit 265. The inter-prediction module 260 and the intra-prediction module 265 may be collectively referred to as a “prediction module”. A dequantizer 220 and an inverse converter 230 may be included in the residual processor.

[87] All or at least a portion of the plurality of components configuring the image decoding equipment 200 may be configured by a hardware component (eg, a decoder or processor) according to an embodiment. In addition, storage device 250 may include a decoded frame buffer (DPB) or may be configured with a digital storage medium.

[88] The image decoding equipment 200, which receives the bit stream including video/image information, can reconstruct the image by performing a process corresponding to the process performed by the image encoding equipment 100 in FIG. 2. For example, the image decoding equipment 200 may perform decoding using a processing unit used in the image encoding equipment. Thus, a decoding processing unit, for example, may be an encoding unit. A coding unit may be obtained by segmenting a coding tree unit or a largest coding unit. The reconstructed image signal decoded and output by the decoding equipment 200 can be reproduced by the playback equipment.

[89] The image decoding equipment 200 may receive a signal output from the image encoding equipment of FIG. 2 in the form of a bitstream. The received signal may be decoded through entropy decoder 210. For example, entropy decoder 210 may parse the bitstream to extract information (eg, video/image information) needed to reconstruct images (or reconstruct frames). The video/image information may further include information regarding various parameter sets, such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. The image decoding equipment may further decode the frame based on information regarding the parameter set and/or general constraint information. The signaling/receiving information and/or syntax elements described in the present disclosure may be decoded by a decoding procedure and obtained from the bit stream. For example, entropy decoder 210 decodes information in a bitstream based on an encoding method, such as exponential Golomb, CAVLC, or CABAC encoding, and the output values of the syntax elements required for image reconstruction and the quantized values of the transform coefficients for the remainder. More specifically, the entropy CABAC decoding method may take a resolution element corresponding to each syntax element in the bitstream, determine a context model using information of a target decoding syntax element, decoding information of an adjacent block and a target decoding block, or information of a symbol/resolution element decoded on a previous one. stage, and perform arithmetic decoding for the resolution element by predicting the probability of occurrence of the permission element according to the determined context model and generating a symbol corresponding to the meaning of each syntactic element. In this case, the entropy CABAC decoding method can update the context model by using the decoded symbol/grant element information for the context model of the next symbol/grant element after determining the context model. The prediction-related information from the information decoded by the entropy decoder 210 may be provided to the prediction module (inter-prediction module 260 and intra-prediction module 265), and the residual value for which entropy decoding is performed in the entropy decoder 210, i.e. quantized conversion coefficients and related parameter information may be input to the dequantizer 220. In addition, information regarding filtering from information decoded by the entropy decoder 210 may be provided to the filter 240. Meanwhile, a receiver (not shown) for receiving a signal output from the equipment image encoding device may be further configured as an internal/external element of image decoding equipment 200, or the receiver may be a component of entropy decoder 210.

[90] Meanwhile, the image decoding equipment according to the present disclosure may be referred to as “video/image/frame decoding equipment.” The image decoding equipment can be classified into an information decoder (video/image/frame information decoder) and a sample decoder (video/image/frame sample decoder). The information decoder may include an entropy decoder 210. The sample decoder may include at least one of a dequantizer 220, an inverse converter 230, an adder 235, a filter 240, a memory 250, an inter-prediction module 260, or an intra-prediction module 265.

[91] Dequantizer 220 may dequantize the quantized transform coefficients and output the transform coefficients. Dequantizer 220 may re-arrange the quantized transform coefficients in the form of a two-dimensional block. In this case, rearrangement may be performed based on the order of coefficient scanning performed in the image encoding equipment. Dequantizer 220 may perform dequantization on the quantized transform coefficients by using a quantization parameter (eg, quantization step size information) and obtain the transform coefficients.

[92] The inverse converter 230 may inversely convert the transform coefficients to obtain a residual signal (residual block, residual sample array).

[93] The prediction module may perform prediction for the current block and may generate a predicted block including prediction samples for the current block. The prediction module may determine whether intra prediction or inter prediction is applied to the current block based on the prediction information output from the entropy decoder 210, and may determine a particular intra/inter prediction mode.

[94] Identical to that described in the prediction module of the image encoding equipment 100, the prediction module can generate a prediction signal based on various prediction methods (techniques), which are described below.

[95] Intra prediction module 265 may predict the current block by reference to samples in the current frame. The description of the intra prediction module 185 applies equally to the intra prediction module 265.

[96] The inter-prediction module 260 may extract a predicted block for the current block based on a reference block (an array of reference samples) indicated by a motion vector for the reference frame. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information may be predicted in units of blocks, sub-blocks or samples based on the correlation of the motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0-prediction, L1-prediction, bi-prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block present in the current frame and a temporal neighbor block present in the reference frame. For example, the inter-prediction module 260 may configure a motion information candidate list based on neighboring blocks and extract the current block's motion vector and/or reference frame index based on the received candidate selection information. The inter-prediction may be performed based on various prediction modes, and the information regarding the prediction may include information indicating the inter-prediction mode for the current block.

[97] The adder 235 may generate a reconstructed signal (recovered frame, reconstructed block, reconstructed sample array) by adding the resulting residual signal with a prediction signal (predicted block, predicted sample array) output from a prediction module (including inter prediction module 260 and /or internal prediction module 265). If there is no remainder for a block to be processed, for example when a skip mode is applied, the predicted block can be used as the reconstructed block. The description of adder 155 is equally applicable to adder 235. Adder 235 may be referred to as a “recovery module” or a “recovered block generator.” The generated reconstructed signal can be used to internally predict the next block to be processed in the current frame, and can be used to inter-predict the next frame through filtering, as described below.

[98] Filter 240 may enhance the subjective/objective quality of images by applying filtering to the reconstructed signal. For example, filter 240 may generate a modified reconstructed frame by applying various filtering techniques to the reconstructed frame and store the modified reconstructed frame in storage device 250, namely, a DPB of storage device 250. Various filtering techniques may include, for example, deblocking filtering. , sampled adaptive bias, adaptive contour filter, bilateral filter, etc.

[99] The (modified) reconstructed frame stored in the DPB of the storage device 250 can be used as a reference frame in the inter-prediction unit 260. Memory 250 may store block motion information from which motion information in the current frame is retrieved (or decoded) and/or motion information of blocks in a frame that have already been reconstructed. The stored motion information may be transmitted to the inter-prediction unit 260 so that it is used as spatial neighbor block motion information or temporal neighbor block motion information. Memory 250 may store reconstructed samples of reconstructed blocks in the current frame and transmit the reconstructed samples to intra prediction module 265.

[100] In the present disclosure, the embodiments described in the filter 160, the inter-prediction module 180, and the intra-prediction module 185 of the image encoding equipment 100 may be equally or correspondingly applied to the filter 240, the inter-prediction module 260, and the intra-prediction module 265 image decoding equipment 200.

[101] General introduction to image segmentation

[102] The video/image encoding method according to the present disclosure can be implemented based on an image segmentation structure as follows. In particular, the prediction, residual processing ((in)transformation, (de)-quantization, etc.), syntax element encoding and filtering procedures described below can be performed on a CTU, CU (and/or TU, PU) basis ), extracted based on the image segmentation structure. The image may be segmented in units of blocks, and the block segmentation procedure may be performed in the image segmentation unit 110 of the encoding equipment. Segmentation-related information may be encoded by entropy encoder 190 and transmitted to decoding equipment in the form of a bit stream. The entropy decoder 210 of the decoding equipment can extract the block segmentation structure of the current frame based on the segmentation-related information obtained from the bit stream, and based on this, can perform a series of procedures (eg, prediction, residual processing, block/frame reconstruction, in-loop filtering, and etc.) for decoding images.

[103] Frames may be segmented into a sequence of coding tree units (CTUs). Fig. 4 shows an example in which a frame is segmented into CTUs. A CTU may correspond to a coding tree block (CTB). Alternatively, the CTU may include a luma sample coding tree block and two coding tree blocks of corresponding chrominance samples. For example, for a frame that contains three sample arrays, the CTU may include a block of NxN luma samples and two corresponding blocks of chroma samples.

[104] CTU segmentation overview

[105] As described above, a coding unit can be obtained by recursively segmenting a coding tree unit (CTU) or largest coding unit (LCU) according to a quadtree/binary tree/ternary tree (QT/BT/TT) structure. For example, a CTU may first be segmented into quadtree structures. Thereafter, the leaf nodes of the quadtree structure can be further segmented by a multi-type tree structure.

[106] Quadtree segmentation means that the current CU (or CTU) is segmented equally into four. Through segmentation according to the quadtree, the current CU can be segmented into four CUs having identical width and identical height. When the current CU is no longer segmented into a quadtree structure, the current CU corresponds to a leaf node of the quadtree structure. The CU corresponding to the leaf node of the quadtree structure can no longer be segmented and can be used as the final encoding unit described above. Alternatively, the CU corresponding to a leaf node of the quadtree structure may further be segmented by a multi-type tree structure.

[107] FIG. 5 is a view showing an embodiment of a block segmentation type according to a multi-type tree structure. Segmentation according to a multi-type tree structure may include two types of partitioning according to a binary tree structure and two types of partitioning according to a ternary tree structure.

[108] Two types of partitioning according to the binary tree structure may include vertical binary partitioning (SPLIT_BT_VER) and horizontal binary partitioning (SPLIT_BT_HOR). Vertical binary splitting (SPLIT_BT_VER) means that the current CU is split equally in half in the vertical direction. As shown in FIG. 4, through vertical binary partitioning, two CUs having a height identical to the height of the current CU and having a width that is half the width of the current CU can be formed. Horizontal binary splitting (SPLIT_BT_HOR) means that the current CU is split equally in half in the horizontal direction. As shown in FIG. 5, through horizontal binary partitioning, two CUs having a height that is half the height of the current CU and having a width identical to the width of the current CU can be formed.

[109] Two types of partitioning according to the ternary tree structure may include vertical ternary partitioning (SPLIT_TT_VER) and horizontal ternary partitioning (SPLIT_TT_HOR). In vertical ternary splitting (SPLIT_TT_VER), the current CU is split in the vertical direction in a ratio of 1:2:1. As shown in FIG. 5, through vertical ternary partitioning, two CUs having a height identical to the height of the current CU and having a width that is 1/4 of the width of the current CU, and a CU having a height identical to the height of the current CU and having a width that is half the width of the current CU. In horizontal ternary splitting (SPLIT_TT_HOR), the current CU is split horizontally in a ratio of 1:2:1. As shown in FIG. 5, through horizontal ternary partitioning, two CUs having a height that is 1/4 of the height of the current CU and having a width identical to the width of the current CU, and a CU having a height that is half the height of the current CU and having width identical to the width of the current CU.

[110] FIG. 6 is a view showing a signaling mechanism for blocking information in a quadtree with a nested multi-type tree structure according to the present disclosure.

[111] Here, the CTU is treated as the root node of a quadtree and is segmented for the first time into a quadtree structure. Information (eg, qt_split_flag) indicating whether or not quadtree splitting is performed for the current CU (CTU or QT_node) is signaled. For example, when qt_split_flag has the first value (for example, "1"), the current CU can be segmented into a quadtree. In addition, when qt_split_flag has a second value (for example, "0"), the current CU is not split into the quadtree, but becomes a leaf node (QT_leaf_node) of the quadtree. Each quadtree leaf node can then be further segmented into multi-type tree structures. Thus, a quadtree leaf node can become a node (MTT_node) of a multi-type tree. In a multi-type tree structure, the first flag (eg, Mtt_split_cu_flag) is signaled to indicate whether or not the current node is further segmented. If the corresponding node is further split (eg, if the first flag is 1), a second flag (eg, Mtt_split_cu_vertical_flag) may be signaled to indicate the direction of the split. For example, the split direction may be a vertical direction if the second flag is 1, and may be a horizontal direction if the second flag is 0. A third flag (for example, Mtt_split_cu_binary_flag) may then be signaled to indicate what represents the split type is a binary partition type or a ternary partition type. For example, the partition type may be a binary partition-based type when the third flag is 1, and may be a ternary partition-based type when the third flag is 0. A node of a multi-type tree obtained by a binary partition or a ternary partition may further be segmented into multi-type tree structures. However, a multi-type tree node may not be segmented into quadtree structures. If the first flag is 0, the corresponding multi-type tree node is no longer split, but becomes a leaf node (MTT_leaf_node) of the multi-type tree. The CU corresponding to a leaf node of a multi-type tree can be used as the final encoding unit described above.

[112] Based on mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, the multi-tree split mode (MttSplitMode) of the CU can be retrieved as shown in Table 1 below. In the following description, the multi-tree split mode may be called "multi-tree split type" or "partition type".

[113] Tab. 1

MttSplitMode mtt_split_cu_vertical_flag mtt_split_cu_binary_flag SPLIT_TT_HOR 0 0 SPLIT_BT_HOR 0 1 SPLIT_TT_VER 1 0 SPLIT_BT_VER 1 1

[114] FIG. 7 is a view showing an example in which a CTU is segmented into multiple CUs by applying a multi-type tree after applying a quadtree. In fig. 7, bold block edges 710 represent quadtree-based segmentation, and remaining block edges 720 represent multi-tree segmentation. The CU may correspond to a coding block (CB). In an embodiment, the CU may include a luma sample encoder and two chrominance sample encoders corresponding to the luma samples. The CB or TB size of the chrominance signal components may be extracted based on the CB or TB size of the luminance signal components according to the component ratio according to the color format (chrominance signal format, e.g., 4:4:4, 4:2 :2, 4:2:0, etc.) frame/image. In the case of a 4:4:4 color format, the CB/TB size of the chrominance signal components may be set to be equal to the CB/TB size of the luma signal components. In the case of a 4:2:2 color format, the width of the CB/TB chrominance components may be set equal to half the width of the CB/TB chrominance components, and the height of the CB/TB chrominance components may be set to be equal to the height of the CB/TB luminance components. In the case of a 4:2:0 color format, the width of the CB/TB chrominance components may be set equal to half the width of the CB/TB chrominance components, and the height of the CB/TB chrominance components may be set to be equal to half the height of the CB/TB luminance components.

[115] In the embodiment, when the CTU size is 128 based on the luminance signal unit samples, the CU size may have a size from 128x128 to 4x4, which is the same size as the CTU. In one embodiment, in the case of a 4:2:0 color format (or chroma format), the CB size of the chrominance signals may be from 64x64 to 2x2.

[116] Meanwhile, in an embodiment, the CU size and the TU size may be identical. Alternatively, a plurality of TUs may be provided in the CU area. The TU size generally represents the size of the transform unit (TB) of component (sampled) luminance signals.

[117] The TU size may be derived based on the largest valid TB size maxTbSize, which is a predetermined value. For example, when the CU size exceeds maxTbSize, a plurality of TUs (TB) having maxTbSize may be retrieved from the CU, and conversion/reconversion may be performed in TU units (TB). For example, the largest allowable TB size for luma signals may be 64×64, and the largest allowable TB size for chrominance signals may be 32×32. If the width or height of a CB segmented according to the tree structure is greater than the largest width or height of the transform, the CB may be automatically (or implicitly) segmented until the TB size limit in the horizontal and vertical directions is satisfied.

[118] In addition, for example, when intra prediction is applied, the intra prediction mode/type may be retrieved in CU (or CB) units, and the procedure for retrieving neighboring reference samples and generating prediction samples can be performed in TU (or TB) units. In this case, one or a plurality of TUs (or TBs) may be provided in one CU (or CB) area, and, in this case, the plurality of TUs or TBs may share the same intra prediction mode/type.

[119] Meanwhile, for the quadtree-based encoding scheme with nested multi-type tree, the following parameters may be signaled as SPS syntax elements from the encoding equipment to the decoding equipment. For example, at least one of CTU-size, which is a parameter representing the size of the quadtree root nodes, MinQTSize, which is a parameter representing the minimum allowed size of the quadtree leaf nodes, MaxBtSize, which is a parameter representing the maximum the allowed size of the root nodes of a binary tree, MaxTtSize, which is a parameter representing the maximum allowed size of the root nodes of a ternary tree, MaxMttDepth, which is a parameter representing the maximum allowed depth of a multi-tree based partition hierarchy from a quadtree leaf node, MinBtSize, which is a parameter representing the minimum allowed size of binary tree leaf nodes, or MinTtSize, which is a parameter representing the minimum allowed size of ternary tree leaf nodes, is signaled.

[120] As an embodiment of using a 4:2:0 chrominance signal format, the CTU size may be set to 128x128 luma blocks and two 64x64 chroma blocks corresponding to luma blocks. In this case, MinOTSize can be set to 16x16, MaxBtSize can be set to 128x128, MaxTtSzie can be set to 64x64, MinBtSize and MinTtSize can be set to 4x4, and MaxMttDepth can be set to 4. Quadtree Segmentation can be applied to a CTU to form quadtree leaf nodes. A quadtree leaf node may be called a "QT leaf node". Quadtree leaf nodes can range in size from 16x16 (for example, MinOTSize) to 128x128 (for example, CTU-size). If the QT leaf node is 128x128, it may not be further segmented into a binary tree/ternary tree. This is due to the fact that in this case, even with segmentation, it exceeds MaxBtsize and MaxTtszie (for example, 64x64). In other cases, QT leaf nodes may further be segmented into a multi-type tree. Therefore, a QT leaf node is the root node for a multi-type tree, and a QT leaf node can have a value of 0 for the multi-type tree depth (mttDepth). If the depth of the multi-type tree reaches MaxMttdepth (for example, 4), additional segmentation may no longer be considered. If the node width of a multi-type tree is MinBtSize and less than or equal to 2xMinTtSize, then additional horizontal segmentation may not be considered. If the node height of a multi-type tree is MinBtSize and less than or equal to 2xMinTtSize, additional vertical segmentation may not be considered. When segmentation is not considered, the encoding equipment may omit the signaling of segmentation information. In this case, the decoding equipment can extract segmentation information with a predetermined value.

[121] Meanwhile, one CTU may include a luminance signal sample encoding unit (hereinafter referred to as a "luminance signal unit") and two chrominance signal sample encoding units corresponding thereto (hereinafter referred to as "chrominance signal units"). The above-described coding tree-based scheme can be applied equally or separately to the luma signal block and the chrominance signal block of the current CU. In particular, luma and chroma blocks in the same CTU may be segmented into an identical block tree structure, in which case, the tree structure is represented as SINGLE_TREE. Alternatively, blocks of luma and chrominance signals in a single CTU may be segmented into separate block tree structures, in which case, the tree structure may be represented as DUAL_TREE. Thus, when a CTU is segmented into dual trees, a block tree structure for a luma block and a block tree for a chrominance block may be separately present. In this case, the block tree structure for the luminance signal block may be called "DUAL_TREE_LUMA", and the block tree structure for the chrominance signal component may be called "DUAL_TREE_CHROMA". For groups of P- and B-slices/tiles, luma and chrominance blocks in the same CTU may be limited to having identical encoding tree structure. However, for groups of I-slices/tiles, luma and chroma blocks may have a separate block tree structure relative to each other. If a separate block tree structure is used, the luma CTB may be segmented into CUs based on a particular coding tree structure, and the chroma CTB may be segmented into chrominance CUs based on a different coding tree structure. Thus, this means that a CU in an I-slice/tile group to which a separate block tree structure is applied may include a luma component encoding unit or two chrominance component encoding units, and CUs of a P- or B- group. slices/tiles may include blocks of three color components (a luma component and two chrominance components).

[122] Although a structure in the form of a quadtree-based coding tree with a nested multi-type tree is described, the structure in which the CU is segmented is not limited to this. For example, a BT structure and a TT structure may be interpreted as a concept included in a multi-partitioning tree (MPT) structure, and a CU may be interpreted as segmentable through a QT structure and an MPT structure. In an example in which the CU is segmented across a QT structure and an MPT structure, a syntax element (for example, MPT_split_type) including information regarding how many blocks the leaf node of the QT structure is segmented into, and a syntax element (for example, MPT_split_mode) , including information regarding in which of the vertical and horizontal directions the leaf node of the QT structure is segmented, may be signaled to determine the segmentation structure.

[123] In another example, the CU may be segmented in a manner different from the QT structure, BT structure, or TT structure. Thus, in contrast to a smaller CU being segmented 1/4 of a larger depth CU according to the QT structure, a shallower CU being segmented 1/2 of a larger depth CU according to the BT structure, or a shallower CU being segmented by 1 /4 or 1/2 of a deeper CU according to the TT structure, a shallower CU can be segmented to 1/5, 1/3, 3/8, 3/5, 2/3 or 5/8 of a deeper CU in some cases, and the CU segmentation method is not limited to this.

[124] The multi-type tree quadtree coding block structure can provide a very flexible block segmentation structure. Due to the segmentation types supported in a multi-type tree, different segmentation patterns can potentially result in an identical encoding block structure in some cases. In the encoding equipment and decoding equipment, by limiting the occurrence of such redundant segmentation patterns, the data amount of segmentation information can be reduced.

[125] For example, FIG. 8 shows the redundant partitioning patterns that can occur in binary tree partitioning and ternary tree partitioning. As shown in FIG. 8, the continuous binary partition 810 and 820 for one direction of the two-stage layers has a coding block structure identical to the coding block structure for the binary partition for the center segment after the ternary partition. In this case, binary tree splitting for the central ternary tree splitting units 830 and 840 may be prohibited. This prohibition is applicable to all frame CUs. When such a particular partitioning is prohibited, signaling of the corresponding syntax elements may be modified to reflect this prohibited case, thereby reducing the number of bits signaled for partitioning. For example, as shown in the example shown in FIG. 8, when binary splitting for a central CU is disabled, a syntax element mtt_split_cu_binary_flag indicating whether the split is a binary split or a ternary split is not signaled, and its value may be extracted as 0 by the decoding equipment.

[126] Chroma format overview

[127] The format of the chrominance signals is described later in this document. The image may be encoded into encoded data including an array of luma components (eg, Y) and two arrays of chrominance components (eg, Cb and Cr). For example, one pixel of an encoded image may include a luma sample and a chrominance sample. The chrominance signal format may be used to represent the configuration format of the luma signal sample and the chrominance signal sample, and the chrominance signal format may be referred to as a “color format”.

[128] In an embodiment, the image may be encoded into various chrominance signal formats, such as monochrome, 4:2:0, 4:2:2, or 4:4:4. In monochrome sampling, one array of samples may be provided, and the array of samples may be an array of luminance signals. With 4:2:0 sampling, one luma sample array and two chrominance sample arrays may be provided, each of the two chroma arrays may have a height equal to half the height of the luma array and a width equal to half the width of the luma array. With 4:2:2 sampling, one luma sample array and two chrominance sample arrays may be provided, each of the two chroma arrays may have a height equal to the height of the luma array and a width equal to half the width of the luma array. In 4:4:4 sampling, one luma sample array and two chrominance sample arrays may be provided, and each of the two chroma arrays may have a height and width equal to the height and width of the luma array.

[129] For example, in 4:2:0 sampling, the chroma sample may be located below the corresponding luminance sample. In 4:2:2 sampling, the chroma sample may be positioned to overlap the luminance sample corresponding to it. In 4:4:4 sampling, both the luma sample and the chrominance sample may be located at an overlapping position.

[130] The format of the chrominance signals used in the encoding equipment and decoding equipment may be predetermined. Alternatively, the format of the chrominance signals may be signaled from encoding equipment to decoding equipment so that it can be adaptively used in the encoding equipment and decoding equipment. In an embodiment, the format of the chroma signals may be signaled based on at least one of chroma_format_idc or separate_colour_plane_flag. At least one of chroma_format_idc or separate_colour_plane_flag may be signaled through a high-level syntax such as DPS, VPS, SPS, or PPS. For example, chroma_format_idc and separate_colour_plane_flag may be included in the SPS syntax shown in FIG. 9.

[131] Meanwhile, FIG. 10 shows an embodiment of classifying chroma signal formats using chroma_format_idc and separate_colour_plane_flag signaling; chroma_format_idc may be information indicating the chroma signal format applied to the encoded image; separate_colour_plane_flag can indicate whether or not a color array is processed separately in a particular chrominance signal format.

For example, the first value (eg 0) of chroma_format_idc may indicate monochrome sampling. A second value (eg 1) of chroma_format_idc may indicate 4:2:0 sampling. A third value (eg 2) of chroma_format_idc may indicate 4:2:2 sampling. A fourth value (eg 3) of chroma_format_idc may indicate 4:4:4 sampling.

[132] At 4:4:4, the following may apply based on the value of separate_colour_plane_flag. If the value of separate_colour_plane_flag is the first value (for example, 0), each of the two chroma arrays can have a height and width identical to the height and width of the luma array. In this case, the value of ChromaArrayType, indicating the type of the array of chroma samples, may be set to chroma_format_idc. If the value of separate_colour_plane_flag is the second value (eg, 1), arrays of luma samples, Cb samples, and Cr samples can be separately processed and processed along with the monochrome sampled frames. In this case, ChromaArrayType can be set to 0.

[133] Intra prediction for chrominance block

[134] When intra prediction is performed on the current block, prediction relative to the luminance signal component block (luminance signal block) of the current block and prediction relative to the chrominance signal component block (chrominance signal block) can be performed. In this case, the intra prediction mode for the chrominance signal block may be set separately from the intra prediction mode for the luma signal block.

[135] For example, an intra-chroma prediction mode for a chroma block may be indicated based on the intra-chroma prediction mode information, and the intra-chroma prediction mode information may be signaled in the form of an intra_chroma_pred_mode syntax element. For example, the intra-chrominance prediction mode information may represent one of a planar mode, a DC mode, a vertical mode, a horizontal mode, a extracted mode (DM), and a cross-component linear model (CCLM) mode. Here, a planar mode may indicate intra-prediction mode #0, a DC mode may indicate intra-prediction mode #1, a vertical mode may indicate intra-prediction mode #26, and a horizontal mode may indicate intra-prediction mode #10. DM may also be called "direct mode". CCLM can also be called "linear model (LM)". The CCLM mode may include at least one of L_CCLM, T_CCLM and LT_CCLM.

[136] Meanwhile, DM and CCLM are dependent intra prediction modes for predicting a chroma block using information regarding a luma block. The DM may represent a mode in which an intra prediction mode identical to the intra prediction mode for the luma signal component is applied as an intra prediction mode for the chrominance signal component. In addition, CCLM may represent an intra-prediction mode using, as predicted chrominance block samples, samples extracted by subsampling the reconstructed luma block samples and then applying α and β, which are CCLM parameters, to the subsampled samples in the generation process prediction block for the chrominance signal block.

[137] CCLM (Cross Component Linear Model) based mode

[138] As described above, the CCLM mode may be applied to a chrominance block. The CCLM mode is an intra-prediction mode using correlation between a luma block and a chrominance block corresponding to a luma block, and is performed by extracting a linear model based on adjacent samples of the luma block and adjacent samples of the chrominance block. In addition, a predictive chrominance block sample can be extracted based on the extracted linear model and the reconstructed luminance block samples.

[139] In particular, when the CCLM mode is applied to the current chrominance block, parameters for the linear model can be extracted based on the neighboring samples used for intra-prediction of the current chroma block and the neighboring samples used for intra-prediction of the current luminance block. For example, the linear model for CCLM can be expressed based on the following equation.

[140] equation 1

[141] ,

[142] where pred _c (i, j) may denote a predictive sample of coordinates (i, j) of the current chroma block in the current CU; rec _L '(i, j) may denote the reconstructed sample of coordinates (i, j) of the current block of luminance signals in the CU. For example, rec _L '(i, j) may denote a downsampled reconstructed sample of the current block of luminance signals. The coefficients α and β of the linear model can be signaled or extracted from adjacent samples.

[143] Palette mode overview

[144] Palette mode is described later in this document. The encoding equipment according to the embodiment can encode an image using a palette mode, and the decoding equipment can decode an image using a palette mode in a manner corresponding thereto. The palette mode may be called "palette encoding mode", "internal palette mode", "internal palette encoding mode", etc. The palette mode can be considered as a type of intra-coding mode or can be considered as one of the intra-prediction methods. However, similar to the skip mode described above, the individual residual value for the corresponding block may not be signaled.

[145] In an embodiment, palette mode can be used to improve encoding efficiency when encoding screen content that is a computer-generated image that includes a significant amount of text and graphics. In general, a local area of an image generated as screen content is divided by sharp edges and expressed by a small number of colors. To exploit this feature, in palette mode, samples for one block can be expressed by indices indicating the color table entry of the palette.

[146] To employ palette mode, information regarding the palette table may be signaled. In an embodiment, the palette table may include an index value corresponding to each color. To signal the index value, palette index prediction information may be signaled. The palette index prediction information may include an index value for at least a portion of the palette index map. In a palette index map, pixels of video data can be converted into color indexes of a palette table.

[147] The palette index prediction information may include series value information. For at least a portion of the palette index map, the series value information may associate a series value with an index value. One series value can be associated with a color index with a control code. The palette index map may be generated from the palette index prediction information. For example, at least a portion of the palette index map may be generated by determining whether or not to adjust the index value of the palette index prediction information based on the last index value.

[148] The current block in the current frame can be encoded or reconstructed according to the palette index map. When using palette mode, the pixel value in the current encoding unit can be expressed as a small set of representative color values. This set may be called a "palette". For pixels having a value close to the palette color, the palette index may be signaled. For pixels having a value that does not belong to (is outside) the palette, the corresponding pixels may be designated by a control code symbol, and the quantized pixel value may be directly signaled. In this document, a pixel or pixel value may be described as a sample.

[149] To encode a palette-mode encoded block, decoding equipment may decode the color and palette index. A palette color may be described in a palette table and may be encoded using a palette table encoding tool. A control code flag may be signaled for each coding unit. The control code flag may indicate whether or not a control code symbol is present in the current encoding unit. If a control code character is present, the palette table may be incremented by 1 unit (eg, an index unit), and the last index may be designated as the control code encoding mode. The palette indices of all pixels for one encoding unit may configure a palette index map and may be encoded using a palette index map encoding tool.

[150] For example, to encode a palette table, a palette predictor may be supported. The palette predictor can be initialized at the starting point of each slice. For example, the palette predictor may be reset to 0. For each palette predictor entry, a reusable flag indicating whether or not it is part of the current palette may be signaled. The reusable flag may be signaled using run-length encoding of the value as 0.

[151] Thereafter, numbers for new palette entries can be signaled using a zero-order exponential Golomb code. Finally, component values for a new palette entry may be signaled. After encoding the current encoding unit, the palette predictor may be updated using the current palette, and an entry from the previous palette predictor that is not reused in the current palette (before reaching the allowed maximum size) may be appended to the end of the new palette predictor, and this may be called " filling the palette."

[152] For example, to encode a palette index map, the indices may be encoded using horizontal or vertical scanning. The scan order may be signaled via a bitstream using palette_transpose_flag, which is a parameter indicating the scan direction. For example, when a horizontal scan is applied to scan indices for samples in the current encoding unit, palette_transpose_flag may have a first value (eg, 0), and when a vertical scan is applied, palette_transpose_flag may have a second value (eg, 1). Fig. 11 shows an embodiment of horizontal scanning and vertical scanning according to the embodiment.

[153] In addition, in an embodiment, the palette index may be encoded using an "index" mode and a "copy on top" mode. Except for the case in which the palette index mode is signaled for the topmost row when horizontal scanning is used, the case in which the palette index mode is signaled for the leftmost column when vertical scanning is used, and the case in which directly the previous mode is "copy on top", these two modes can be signaled using the same flag.

[154] In "index" mode, the palette index may be explicitly signaled. For the "index" mode and the "copy on top" mode, a run value indicating the number of pixels encoded using the identical mode may be signaled.

[155] The encoding order for the index map can be set as follows. First, the number of index values for a coding unit may be signaled. This may be done after signaling the actual index value for the entire coding unit using truncated binary coding. Both index numbers and index values can be encoded in bypass mode. Due to this, bypass permission elements associated with the index can be grouped. The palette mode ("index" or "copy on top") and the run value can then be signaled using an interleaving technique.

[156] Finally, the component control code values corresponding to the control code samples for the entire coding unit may be mutually grouped and bypassed; last_run_type_flag, which is an optional syntax element, may be signaled after the index value is signaled. By using last_run_type_flag along with the number of indices, signaling the run value corresponding to the last run in the block can be skipped.

[157] In an embodiment, a bitree type in which independent coding unit segmentation is performed for the luma signal component and the chrominance signal component may be used for the I-slice. The palette mode can be applied to the luma signal component and the chrominance signal component separately or together. If split wood is not used, palette mode applies to all Y, Cb and Cr components.

[158] In an embodiment, the syntax element for palette mode may be encoded and signaled as shown in FIG. 12-19. Fig. 12-13 show the sequential syntax in a coding unit (CU) for palette mode, and FIG. Figures 14-19 show the sequential syntax for palette mode.

[159] Each syntactic element is described later in this document; pred_mode_plt_flag, which is a palette mode flag, may indicate whether or not the palette mode is applied to the current encoding unit. For example, the first value (eg, 0) of pred_mode_plt_flag may indicate that the palette mode is not applied to the current encoding unit. A second value (eg, 1) of pred_mode_plt_flag may indicate that the palette mode is applied to the current encoding unit. When pred_mode_plt_flag is not obtained from the bit stream, the value of pred_mode_plt_flag may be determined to constitute the first value.

[160] The PredictorPaletteSize[startComp] parameter can specify the size of the predictor palette for startComp, which is the first color component of the current palette table.

[161] The PalettePredictorEntryReuseFlags[i] parameter may be information indicating whether or not the entry should be reused. For example, the first value (e.g., 0) of PalettePredictorEntryReuseFlags[i] may indicate that the i-th predictor palette entry may indicate that the i-th predictor palette entry is not the current palette entry, and the second value (e.g., 1) may indicate that the i-th entry in the predictor palette can be reused in the current palette. To use PalettePredictorEntryReuseFlags[i], the initial value can be set to 0.

[162] The palette_predictor_run parameter can specify the number of zeros present before a non-zero entry in the PalettePredictorEntryReuseFlags array.

[163] The num_signalled_palette_entries parameter can specify the number of entries in the current palette explicitly signaled for the first startComp color component of the current palette table. When num_signalled_palette_entries is not obtained from the bitstream, the value of num_signalled_palette_entries may be defined to be 0.

[164] The CurrentPaletteSize[startComp] parameter can specify the current palette size for the first startComp color component of the current palette table. This can be calculated as shown in the following equation. CurrentPaletteSize[startComp] can range from 0 to palette_max_size.

[165] equation 2

[166] CurrentPaletteSize[startComp]=NumPredictedPaletteEntries+num_signalled_palette_entries

[167] The new_palette_entries[cIdx][i] parameter may indicate the value of the palette entry signaled in the i-th color component cIdx.

[168] The PredictorPaletteEntries[cIdx][i] parameter can specify the i-th element in the predictor palette for the cIdx color component.

[169] The CurrentPaletteEntries[cIdx][i] parameter can specify the i-th element in the current palette for the cIdx color component. PredictorPaletteEntries and CurrentPaletteEntries may be formed as shown in the equation of FIG. 20.

[170] The palette_escape_val_present_flag parameter may indicate whether an escape code encoding sample is present or not. For example, a first value (eg, 0) of palette_escape_val_present_flag may indicate that a control code encoding sample is present for the current coding unit, and a second value (eg, 1) of palette_escape_val_present_flag may indicate that the current coding unit includes at least one control code encoding sample. When palette_escape_val_present_flag is not obtained from the bitstream, the value of palette_escape_val_present_flag may be defined to be 1.

[171] The MaxPaletteIndex parameter can indicate the maximum available palette index value for the current encoding unit. The MaxPaletteIndex value can be set to CurrentPaletteSize[startComp]+palette_escape_val_present_flag.

[172] The num_palette_indices_minus1 parameter can specify the number of palette indices to be signaled explicitly or implicitly for the current block. For example, the value obtained by summing 1 with num_palette_indices_minus1 may indicate the number of palette indices explicitly or implicitly signaled for the current block. When num_palette_indices_minus1 is not included in the bitstream, the value of num_palette_indices_minus1 may be defined to be 0.

[173] The palette_idx_idc parameter may be an index indicator for the CurrentPaletteEntries table of palettes. The palette_idx_idc value may have a value from 0 to MaxPaletteIndex for the first index of the corresponding block, and may have a value from 0 to MaxPaletteIndex-1 for the remaining indices of the corresponding block. When the palette_idx_idc value is not obtained from the bitstream, the palette_idx_idc value may be defined to be 0.

[174] The PaletteIndexIdc[i] parameter may be an array storing the value of the i-th palette_idx_idc signaled explicitly or implicitly. The values of all PaletteIndexIdc[i] elements can be initialized to 0.

[175] The copy_above_indices_for_final_run_flag parameter may indicate information indicating whether or not the previous index for the last run should be copied, the first value (for example, 0) may indicate that the palette index at the last position of the current encoding unit is explicitly or implicitly signaled via bitstream, and the second value (eg, 1) may indicate that the palette index at the last position of the current encoding unit is explicitly or implicitly signaled through the bitstream. When copy_above_indices_for_final_run_flag is not obtained from the bitstream, the value of copy_above_indices_for_final_run_flag may be defined to be 0.

[176] The palette_transpose_flag parameter may be information indicating a scanning method used to scan the index for a pixel of the current encoding unit. For example, the first value (eg, 0) of palette_transpose_flag may indicate that horizontal scanning is used to scan the index for the pixel of the current encoding unit, and the second value (eg, 1) of palette_transpose_flag may indicate that vertical scanning is used to to scan the index for the pixel of the current encoding unit. When palette_transpose_flag is not obtained from the bitstream, the value of palette_transpose_flag may be defined to be 0.

[177] The first value (eg, 0) of the copy_above_palette_indices_flag parameter may indicate that the indicator indicating the index of the sampling palette is obtained or extracted from the encoded bitstream value. A second value (eg 1) copy_above_palette_indices_flag may indicate that the palette index is identical to the palette index of an adjacent selection. For example, the adjacent sample may be a sample located at a position identical to the position of the current sample in the left column of the current sample when vertical scanning is currently in use. Alternatively, the adjacent sample may be a sample located at a position identical to the position of the current sample in the top row of the current sample when horizontal scanning is currently in use.

[178] The first value (eg, 0) of the CopyAboveIndicesFlag[xC][yC] parameter may indicate that the palette index is derived explicitly or implicitly from the bitstream. The second value (eg, 1) may indicate that the palette index is generated by copying the left column palette index when vertical scanning is currently in use, or by copying the top row palette index when horizontal scanning is currently in use. Here, xC and yC are coordinate indicators relatively indicating the position of the current sample relative to the top left sample of the current frame. PaletteIndexMap[xC][yC] can have a value from 0 to (MaxPaletteIndex-1).

[179] The PaletteIndexMap[xC][yC] parameter can specify the index of the palette and, for example, specify the index for an array represented by CurrentPaletteEntries. The xC and yC array indices are coordinate indicators indicating the coordinates of the current sample relative to the top-left sample of the current frame, as described above. PaletteIndexMap[xC][yC] can have a value from 0 to (MaxPaletteIndex-1).

[180] The PaletteRun parameter can indicate the number of consecutive positions having an identical palette index when the value of CopyAboveIndicesFlag[xC][yC] is 0. Meanwhile, when the value of CopyAboveIndicesFlag[xC][yC] is 1, PaletteRun can indicate the number of consecutive positions having a palette index identical to the palette index at the position in the top row when the current scan direction is a horizontal scan, and the palette index at the position in the left column when the current scan direction is a vertical scan.

[181] The PaletteMaxRun parameter can specify the maximum PaletteRun value available. The PaletteMaxRun value can be an integer greater than 0.

[182] The palette_run_prefix parameter can specify the prefix portion used to convert to PaletteRun binary form.

[183] The palette_run_suffix parameter can specify the suffix part used to convert to PaletteRun binary form. When palette_run_suffix is not obtained from the bitstream, its value may be defined to be 0.

[184] The value of PaletteRun can be determined as follows. For example, when the value of palette_run_prefix is less than 2, it can be calculated as follows.

[185] equation 3

[186] PaletteRun=palette_run_prefix

[187] Otherwise, when the value of palette_run_prefix is equal to or greater than 2, it may be calculated as follows.

[188] equation 4

[189] PrefixOffset=1<<(palette_run_prefix-1)

[190] PaletteRun=PrefixOffset+palette_run_suffix

[191] The palette_escape_val parameter may indicate a quantized escape code encoding sample value for the component. The PaletteEscapeVal[cIdx][xC][yC] parameter may specify a value with a sampling control code with a value of PaletteIndexMap[xC][yC] (MaxPaletteIndex-1) and a palette_escape_val_present_flag value of 1. Here, cIdx may indicate a color component. The xC and yC array indicators may be position indicators indicating the relative distances of the position of the current sample from the top left sample of the current frame, as described above.

[192] Color Prediction Mode Signaling When Using Palette Mode

[193] This document further describes a method for signaling chrominance signal prediction mode information when using a palette mode. In an embodiment, predictive chroma coding, such as CCLM, may not be applied to the coding unit (or coding block) to which the palette mode is applied. In addition, intra_chroma_pred_mode may not be signaled for the coding unit to which the palette mode is applied.

[194] When determining that CCLM is available for a chroma component, an enable/disable flag for it may be signaled. In an embodiment, CCLM availability may be determined using sps_palette_enabled_flag or sps_plt_enabled_flag, and the CCLM enable/disable flag may be signaled using sps_palette_enabled_flag or sps_plt_enabled_flag.

[195] Meanwhile, in the example of FIG. 13, the signaling of CCLM information (eg, cclm_mode_flag) does not consider whether or not the palette mode of the coding unit should be applied. For example, in the example of FIG. 13, an embodiment is described in which predetermined chroma prediction information (e.g., cclm_mode_flag, intra_chroma_pred_mode) is signaled when the palette mode is not applied to the current coding unit, or when the coding unit is not a dual-structured chroma signal. tree.

[196] In this case, since the predetermined chrominance signal prediction information is signaled in a palette-mode encoded block in a single tree, unnecessary signaling in syntax signaling may occur. In addition, since predetermined chrominance prediction information is carried in overhead signals, even if the chrominance signal component in a coding unit is encoded in palette mode, intra-chrominance prediction according to CCLM can be performed, and intra-chrominance prediction according to DM mode can be performed.

[197] To solve the above problem, the syntax for a coding unit may be modified as shown in FIG. 21. Fig. 21 shows a coding unit syntax indicating that predetermined intra-chroma signal prediction information 2120 is obtained from the bit stream when the value of pred_mode_plt_flag 2110, which is a parameter indicating whether or not a palette mode is applied to the current coding unit, is the first value ( for example, 0), indicating that the palette mode is not applied. In addition, the syntax of FIG. 21 indicates that predetermined intra-chroma signal prediction information 2120 is not obtained from the bit stream when the value of pred_mode_plt_flag 2110 is a second value (eg, 1) indicating that the palette mode is applied.

[198] Similar to the embodiment of FIG. 21, to carry predefined chroma prediction information (eg, cclm_mode_flag, intra_chroma_pred_mode) in overhead signals, predefined chroma prediction information (eg, cclm_mode_flag, intra_chroma_pred_mode) may be carried in overhead signals depending on whether or not a palette mode is applied to current coding unit.

[199] Hereinafter, this document describes the signaling of predetermined intra-chrominance signal prediction information according to the syntax of FIG. 21 with reference to FIG. 22. The encoding equipment or decoding equipment according to an embodiment can determine whether or not the palette mode is applied to the current encoding unit (eg, an encoding block) (S2210). For example, the decoding equipment may determine whether or not the palette mode is applied to the current encoding unit according to the value of pred_mode_plt_flag.

[200] Then, when the palette mode is applied to the current encoding unit, the encoding equipment can encode the corresponding encoding unit in the palette mode, and the decoding equipment can decode the corresponding encoding unit in the palette mode. Therefore, the encoding equipment or the decoding equipment may not transmit predetermined color signal prediction information in the signaling signals (S2220). For example, the encoding equipment may not encode predetermined chroma prediction information (eg, cclm_mode_flag, intra_chroma_pred_mode), and the decoding equipment may not obtain predetermined chroma prediction information from the bit stream.

[201] Then, when the palette mode is not applied to the current encoding unit, the encoding equipment or decoding equipment may signal predetermined chrominance signal prediction information. In an embodiment, the encoding equipment or the decoding equipment may determine whether or not a CCLM mode is available for the current encoding unit (S2230), signal the CCLM parameter, if any (S2240), and signal the intra_chroma_pred_mode parameter, in its absence (S2250).

[202] To this end, the step of obtaining chrominance signal prediction information by the decoding equipment will be described in more detail in the following with reference to FIG. 23. When the palette mode is not applied to the current coding unit (S2310), the decoding equipment can determine whether or not the CCLM mode is available for the current coding unit (S2320). For example, the sps_cclm_enabled_flag parameter indicating the availability of the CCLM mode signaled in the sequence parameter set has a first value (e.g., 0) indicating that the CCLM mode is not available, the decoding equipment may determine that the CCLM mode is not available for the current coding unit. Alternatively, when sps_cclm_enabled_flag has a second value (for example, 1) indicating that CCLM mode is enabled, the sh_slice_type slice type parameter passed through the slice header indicates that the current slice type is not an I-slice, or the size of the signal component If the luminance of the current block is less than 64, the decoding equipment may determine that CCLM mode is available for the current encoding unit. Alternatively, when sps_cclm_enabled_flag has a second value (e.g., 1) indicating that CCLM mode is enabled, each coding tree unit (CTU) in which the sps_qtbtt_dual_tree_intra_flag signaled in the sequence parameter set is included in an I-slice is split into luma component blocks having a size of 64x64, and it does not indicate that each CTU becomes a dual-tree header node, the decoding equipment may determine that the CCLM mode is available for the current coding unit.

[203] When the CCLM mode is available, the decoding equipment can determine whether or not CCLM is applied to the current encoding unit (S2330). For example, decoding equipment may obtain the cclm_mode_flag parameter from the bitstream. The cclm_mode_flag parameter can indicate whether or not CCLM mode should be used. The first value (eg 0) of cclm_mode_flag may indicate that CCLM mode is not applied. A second value (eg, 1) of cclm_mode_flag may indicate that a CCLM mode in the form of any of T_CCLM, L_CCLM, and LT_CCLM is applicable. When the value of cclm_mode_flag is not obtained from the bit stream, the value of cclm_mode_flag may be defined to be 0.

[204] When applying the CCLM mode (eg, cclm_mode_flag==1), the decoding equipment may obtain the cclm_mode_idx parameter from the bitstream (S2340). The cclm_mode_idx parameter may specify an index indicating the CCLM mode used to decode the chrominance signal component of the current coding unit, from T_CCLM, L_CCLM and LT_CCLM.

[205] Meanwhile, when the CCLM mode is not available or the CCLM mode is not applied (eg, cclm_mode_flag==0), the decoding equipment may obtain the intra_chroma_pred_mode parameter from the bitstream (S2350). As described above, the intra_chroma_pred_mode parameter may indicate the intra prediction mode used to decode the chroma signal component of the current coding unit. For example, intra_chroma_pred_mode may indicate one of planar mode, DC mode, vertical mode, horizontal mode, and extracted mode (DM).

[206] Coding method

[207] Hereinafter, this document will describe a method for performing encoding by the encoding equipment according to the embodiment using the above-described method with reference to FIG. 24. The encoding equipment according to the embodiment includes a memory and at least one processor, and the at least one processor can implement the following encoding method.

[208] First, the encoding equipment may determine the current block by dividing the image (S2410). For example, the encoding equipment may determine the current block by dividing the image, as described above with reference to FIG. 4-6. In the partitioning process according to the embodiment, the image partition information may be encoded, and the encoded image partition information may be generated as a bit stream.

[209] Next, the encoding equipment may determine a prediction mode of the current block (S2420). Thereafter, the encoding equipment may encode a palette mode flag (eg, pred_mode_plt_flag) indicating that the prediction mode of the current block is a palette mode based on whether the prediction mode of the current mode is a palette mode or not (S2430). The encoded palette mode flag may be generated as a bit stream.

[210] Next, the encoding equipment may encode palette mode encoding information in which the current block is coded in palette mode based on the tree type of the current block and whether the prediction mode of the current block is palette mode or not (S2440). For example, when determining that palette mode is applied, the encoding equipment may generate a bitstream by generating palette mode encoding information using palette_coding() syntax, as described with reference to FIG. 14-19.

[211] Meanwhile, encoding the palette mode encoding information of the current block may include encoding the palette mode encoding information of the luminance signal component of the current block. For example, when the tree type of the current block is a single tree type or a luminance signal type with a dual tree structure, and a palette mode is applied to the current block, information for palette mode prediction of a luminance signal component of the current block may be encoded, and a bitstream may be generated using encoded information.

[212] In this case, palette mode encoding information of the luminance signal component of the current block may be encoded based on the block size of the luminance signal components of the current block. For example, similar to the embodiment of FIG. 13, the encoding equipment may generate palette mode encoding information as a bitstream according to a palette_coding() syntax specified based on the width (eg, cbWidth) of the luma component block of the current block and the height (eg, cbHeight) of the luma component block of the current block.

[213] In addition, encoding the palette mode encoding information of the current block may further include encoding the palette mode encoding information of the chrominance signal component of the current block. For example, when palette mode is applied to the current block, and the tree type of the current block is a chrominance signal type with a dual-tree structure, information for palette mode prediction of the chrominance signal component of the current block may be encoded, and a bitstream may be generated using the encoded information .

[214] In this case, palette mode encoding information of the chrominance component of the current block may be encoded based on the block size of the chrominance components of the current block. For example, similar to the embodiment of FIG. 13, the encoding equipment can generate palette mode encoding information as a bitstream according to a palette_coding() syntax specified based on the width (eg, cbWidth/subWidthC) of the chroma component block of the current block and the height (eg, cbHeight/subHeightC) of the component block. chrominance signal of the current block. Here, subWidthC and subHeightC may represent the ratios of the height and width of the luma component block relative to the chrominance component block. In an embodiment, subWidthC and subHeightC may be determined based on chroma_format_idc and separate_cour_plane_flag, as shown in FIG. 10.

[215] Then, when the prediction mode of the current block is not a palette mode, the encoding equipment can encode chrominance component prediction information of the current block (S2450). The chroma component prediction information may be CCLM (Cross Component Linear Model) prediction information (eg, cclm_mode_flag, cclm_mode_idx) or intra-chroma component prediction information (eg, intra_chroma_pred_mode).

[216] Meanwhile, when the palette mode is applied to the current block, the encoding equipment may not encode chrominance signal component prediction information.

[217] More specifically, information regarding CCLM prediction may include a CCLM flag (eg, cclm_mode_flag) indicating whether or not CCLM prediction is performed, and a CCLM mode index (eg, cclm_mode_idx) indicating the CCLM prediction mode . The CCLM flag may be encoded and generated as a bitstream when CCLM prediction is available for the current block. The CCLM mode index may be encoded and generated as a bit stream when the CCLM flag indicates that CCLM prediction is being performed.

[218] Meanwhile, when the CCLM flag indicates that CCLM prediction is not performed, intra-chroma component prediction information (eg, intra_chroma_pred_mode) may be encoded and generated as a bit stream.

[219] Decoding method

[220] Hereinafter, this document will describe a method for performing decoding by the decoding equipment according to the embodiment using the above-described method with reference to FIG. 25. The decoding equipment according to the embodiment may include a storage device and at least one processor, and the at least one processor may implement the following decoding method.

[221] First, the decoding equipment may determine the current block by dividing the image (S2510). For example, the decoding equipment may determine the current block by dividing the image, as described above with reference to FIG. 4-6. In the partitioning process according to the embodiment, image partitioning information obtained from the bit stream may be used.

[222] Next, the decoding equipment can identify whether or not the palette mode is applied for the current block based on the palette mode flag (eg, pred_mode_plt_flag) obtained from the bitstream (S2520).

[223] Thereafter, the decoding equipment can obtain palette mode encoding information of the current block from the bitstream based on the tree type of the current block and whether or not palette mode is applied to the current block (S2530). For example, when determining that palette mode is applied, the decoding equipment may obtain palette mode encoding information from the bit stream using palette_coding() syntax, as described with reference to FIG. 14-19.

[224] Meanwhile, obtaining palette mode encoding information of the current block may include obtaining palette mode encoding information of a luminance signal component of the current block. For example, when the tree type of the current block is a single tree type or a luminance signal type with a dual tree structure, and palette mode is applied to the current block, information for palette mode prediction of the luminance signal component of the current block can be obtained from the bitstream.

[225] In this case, palette mode encoding information of the luminance signal component of the current block can be obtained based on the block size of the luminance signal components of the current block. For example, similar to the embodiment of FIG. 13, the palette_coding() syntax may be performed based on the width (eg, cbWidth) of the luma component block of the current block and the height (eg, cbHeight) of the luma component block of the current block.

[226] Meanwhile, obtaining palette mode encoding information of the current block may further include obtaining palette mode encoding information of a chrominance signal component of the current block. For example, when palette mode is applied to the current block, and the tree type of the current block is a dual-tree chrominance signal type, information for palette mode prediction of the chrominance signal component of the current block can be obtained from the bit stream.

[227] In this case, palette mode encoding information of the chrominance component of the current block can be obtained based on the block size of the chrominance components of the current block. For example, similar to the embodiment of FIG. 13, the palette_coding() syntax may be performed based on the width (eg, cbWidth/subWidthC) of the chrominance component block of the current block and the height (eg, cbHeight/subHeightC) of the chrominance component block of the current block. Here, subWidthC and subHeightC may represent the ratios of the height and width of the luma component block relative to the chrominance component block. In an embodiment, subWidthC and subHeightC may be determined based on chroma_format_idc and separate_colour_plane_flag, as shown in FIG. 10.

[228] Then, when the palette mode is not applied to the current block, the decoding equipment can obtain chrominance component prediction information of the current block from the bit stream (S2540). For example, when palette mode is not applied, the decoding equipment may obtain CCLM prediction information (eg, cclm_mode_flag, cclm_mode_idx) or intra-chroma component prediction information (eg, intra_chroma_pred_mode) from the bitstream, as described with reference to FIG. 23. Meanwhile, when the palette mode is not applied to the current block, chroma component prediction information may not be obtained from the bit stream.

[229] More specifically, the CCLM prediction information may include a CCLM flag (eg, cclm_mode_flag) indicating whether CCLM prediction is performed or not, and a CCLM mode index (eg, cclm_mode_idx) indicating the CCLM prediction mode . The CCLM flag may be obtained from the bitstream when CCLM prediction is available for the current block. The CCLM mode index may be obtained from the bit stream when the CCLM flag indicates that CCLM prediction is being performed.

[230] Meanwhile, when the CCLM flag indicates that CCLM prediction is not performed, intra-chroma component prediction information (eg, intra_chroma_pred_mode) can be obtained from the bitstream.

[231] Application option

[232] Although the exemplary methods of the present disclosure described above are presented as a sequence of operations for clarity of description, it is not intended to limit the order in which the steps are performed, and the steps may be performed simultaneously or in a different order as necessary. To implement the method of the present disclosure, the described steps may further include other steps, may include the remaining steps except some steps, or may include other additional steps except some steps.

[233] In the present disclosure, image encoding equipment or image decoding equipment that performs a predetermined operation (step) may perform an operation (step) of confirming a condition or situation for executing the corresponding operation (step). For example, if it is described that a predetermined operation is performed when a predetermined condition is satisfied, the image encoding equipment or the image decoding equipment may perform the predetermined operation after determining whether or not the predetermined condition is satisfied.

[234] The various embodiments of the present disclosure are not intended to be a list of all possible combinations and are intended to describe characteristic aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more of them.

[235] Various embodiments of the present disclosure may be implemented in hardware, firmware, software, or a combination of the above. If the present disclosure is implemented in hardware, the present disclosure may be implemented in application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays. (FPGA), general processors, controllers, microcontrollers, microprocessors, etc.

[236] In addition, the image decoding equipment and image encoding equipment to which embodiments of the present disclosure apply may be included in a multimedia broadcast transceiver device, a mobile communication terminal, a home theater system video device, a digital cinema system video device, a surveillance camera, video chat device, real-time communication device such as video communication, mobile streaming device, storage medium, video recording camera, video-on-demand (VoD) service device, OTT video device ( video over networks), Internet streaming service device, 3D video device, video telephony system video device, medical video device, etc. and can be used to process video or data signals. For example, OTT video devices may include a game console, Blu-ray player, Internet-enabled television, home theater system, smartphone, tablet PC, digital video recorder (DVR), etc.

[237] FIG. 26 is a view showing a content streaming system to which an embodiment of the present disclosure is applicable.

[238] Referring to FIG. 26, the content streaming system to which the embodiment(s) of this document applies may mainly include an encoding server, a streaming server, a web server, a media storage device, a user device, and a media input device.

[239] The encoding server compresses content input from media input devices such as a smartphone, camera, video recorder, etc. into digital data to form a bit stream, and transmits the bit stream to the streaming server. As another example, when media input devices such as smartphones, cameras, video recorders, etc. directly generate a bit stream, the encoding server may be omitted.

[240] The bitstream may be generated by an image encoding method or image encoding equipment to which an embodiment of the present disclosure is applied, and the streaming server may temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[241] The streaming server transmits multimedia data to the user device based on the user's request through the web server, and the web server serves as a medium for informing the user regarding the service. When a user requests a desired service from a web server, the web server may deliver it to the streaming server, and the streaming server may stream the media data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server serves to manage the command/response between devices in the content streaming system.

[242] The streaming server may receive content from a media storage and/or encoding server. For example, when content is received from an encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bit stream for a predetermined time.

[243] Examples of a user device may include a mobile phone, a smartphone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable media player (PMP), a navigation device, a tablet PC, tablet PCs, ultrabooks, wearable devices (such as smart watches, smart glasses, head-mounted displays), digital TVs, desktop computers, digital signage system, etc.

[244] Each server in a content streaming system may operate as a distributed server, in which case data received from each server may be distributed.

[245] The scope of the disclosure includes software or computer executable instructions (e.g., operating system, application, firmware, program, etc.) to enable operations according to the methods of various embodiments in hardware or computer, non-transitory computer readable media having such software or instructions stored and executed in hardware or a computer.

Industrial applicability

[246] Embodiments of the present disclosure may be used to encode or decode an image.

Claims (40)

1. An image decoding method carried out by image decoding equipment, wherein the image decoding method comprises the steps of: determining the current block by dividing the image; identifying whether or not the palette mode is applied for the current block based on the palette mode flag obtained from the bit stream; obtaining palette mode encoding information of the current block from the bit stream, based on the tree type of the current block and whether palette mode is applied to the current block; And obtaining prediction information for chrominance signal components of the current block from the bitstream based on a palette mode not applied to the current block. 2. The method of decoding images according to claim 1, wherein obtaining palette mode encoding information of the current block comprises obtaining palette mode encoding information of a luminance signal component of the current block, and wherein information for palette mode prediction of the luminance signal component of the current block is obtained from the bitstream based on the tree type of the current block being a single tree type or a luminance signal type with a dual tree structure, and the palette mode applied to the current block. 3. The image decoding method of claim 2, wherein obtaining palette mode encoding information of the luminance signal component of the current block is performed based on the block size of the luminance signal components of the current block. 4. The method of decoding images according to claim 1, wherein obtaining palette mode encoding information of the current block comprises obtaining palette mode encoding information of a chrominance signal component of the current block, and wherein information for palette mode prediction of the chrominance signal component of the current block is obtained from the bit stream based on the palette mode applied to the current block and the tree type of the current block, which is a dual-tree structured chrominance signal type. 5. The method of decoding images according to claim 4, wherein obtaining palette mode encoding information of the chrominance component of the current block is performed based on the block size of the chrominance components of the current block. 6. The method of decoding images according to claim 1, wherein the chrominance component prediction information is cross-component linear model (CCLM) prediction information or intra-chrominance component prediction information. 7. The method of decoding images according to claim 6, wherein the CCLM prediction information comprises a CCLM flag indicating whether CCLM prediction is performed or not, and a CCLM mode index indicating a CCLM prediction mode, wherein the CCLM flag is obtained from the bit stream based on the CCLM prediction available for the current block, and wherein the CCLM mode index is obtained from the bitstream based on the CCLM flag indicating that CCLM prediction is performed. 8. The method of decoding images according to claim 7, wherein intra-chrominance component prediction information is obtained from the bitstream based on a CCLM flag indicating that CCLM prediction is not performed. 9. Image decoding equipment containing: Memory device; And at least one processor, wherein at least one processor is configured to: determine the current block by splitting the image; identify whether or not the palette mode is applied for the current block based on the palette mode flag obtained from the bit stream; obtain palette mode encoding information of the current block from the bit stream, based on the tree type of the current block and whether or not palette mode is applied to the current block; And obtain prediction information for the chrominance signal components of the current block from the bit stream, based on a palette mode not applied to the current block. 10. An image encoding method carried out by image encoding equipment, wherein the image encoding method comprises the steps of: determining the current block by dividing the image; determine the prediction mode of the current block; encoding a palette mode flag indicating whether the current block's prediction mode is a palette mode or not, based on whether the current block's prediction mode is a palette mode; encoding palette mode encoding information in which the current block is palette mode encoded based on the tree type of the current block and whether the prediction mode of the current block is a palette mode or not; And encoding prediction information of the chrominance signal components of the current block based on a prediction mode of the current block that is not a palette mode. 11. The image encoding method of claim 10, wherein the chrominance component prediction information is cross-component linear model (CCLM) prediction information or intra-chrominance component prediction information. 12. Image encoding method according to claim 10, wherein the palette mode encoding information in which the chrominance signal component of the current block is palette-mode encoded is encoded based on the palette mode applied to the current block and the tree type of the current block, which is a chrominance signal type with a dual-tree structure, And wherein the cross-component linear model (CCLM) prediction information or intra-chrominance component prediction information is encoded as chrominance component prediction information based on a palette mode not applied to the current block.

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